Method of exposing a semiconductor wafer and exposure apparatus

ABSTRACT

An exposure apparatus includes an autofocus scan processor configured to generate a detection signal indicating a defocused portion of a resist film over a semiconductor substrate, an exposure scan processor configured to perform an exposure process for the resist film, and a controller configured to feed back the detection signal from the autofocus scan processor to the exposure scan processor.

The present application is a Continuation Application of U.S. patentapplication Ser. No. 13/067,139, filed on May 11, 2011, which is basedon and claims priority from Japanese Patent Application No. 2010-111170,filed on May 13, 2010, the entire contents of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosure relates to a method of exposing a semiconductor wafer andan exposure apparatus for semiconductor wafer.

2. Description of the Related Art

In recent years, with the increase in the diameter of semiconductorwafers in the semiconductor manufacturing process, in order to reducethe cost of the lithographic exposure process used to form resistpatterns, there has been an increase in the shot surface area. However,because of the reduction of the DOF (depth of focus) and adoption ofmicropatterns, there tends to be defocusing, making it difficult toachieve high manufacturing yield. This defocusing refers to theout-of-focus condition (defocusing) during lithographic exposure, causedby unwanted matter on the rear surface of the wafer mainly in thesemiconductor manufacturing process, accompanied by a reduction in theplanarity of the surface of the wafer.

In the lithographic exposure process step, if the above-mentioned typeof defocused portion occurs on the surface of the semiconductor wafer,it is not possible to form a normal resist pattern, and subsequentlythere is a risk of forming abnormalities in, for example, aninterconnect pattern formed using the resist pattern. For example, if anabnormal resist pattern is used to form a system of interconnects(interconnect pattern), the interconnects can become thinned and peel,and this can affect even normal chips in the surrounding area. Also, ifan abnormal resist pattern is used to form holes, the hole diametercould increase and may result in such effects as the sinking of theinterlayer film in subsequent process steps.

In the case of patterning a photoresist film on a wafer usinglithographic projection exposure, the wafer is generally placed onto astage and the height is measured over the entire surface of the wafer,using an autofocus sensor. Then, based on the results of the heightmeasurements, the focus is adjusted during the exposure processing, andexposure processing is performed while controlling the stage or thelike, so that the surface of the wafer is as parallel as possible withthe exposure apparatus. These are disclosed in Japanese PatentApplication Publications Nos. JP-A 10-270317 and JP-A 1-264220.

The exposure method and exposure apparatus described in Japanese PatentApplication Publications Nos. JP-A 10-270317 and JP-A 1-264220 areconfigured so that a defocused portion occurring as the result ofunwanted matter as mentioned above can be detected by an autofocus scan.According to Japanese Patent Application Publication No. JP-A 10-270317,by issuing an alarm when a defocused portion is detected on the wafer,it is possible to prevent exposure processing from proceeding at thatpoint. According to Japanese Patent Application Publication No. JP-A1-264220, when a defocused portion is detected on the wafer, theexposure in the direction of movement is stopped, and exposure isperformed in the direction that is reversed from the direction ofmovement, so that there is no poor resolution within the region on thesubstrate.

In the method and apparatus of Japanese Patent Application PublicationsNos. JP-A 10-270317 and JP-A 1-264220, however, if a defocused portionis detected on the wafer, either an alarm is issued to prompt anoperator to stop the exposure processing or the exposure processingdirection is reversed. For this reason, in Japanese Patent ApplicationPublications Nos. JP-A 10-270317 and JP-A 1-264220, similar to the casedescribed above, it is not possible to form a normal resist pattern atthe defocused portions on the wafer, and abnormal interconnect patternsor holes are formed, and this can affect even surrounding normal chips.Also, with the art of Japanese Patent Application Publications Nos. JP-A10-270317 and JP-A 1-264220, stopping the exposure processing orreversing the processing direction reduces the semiconductor waferproductivity.

In the related art, including that of Japanese Patent ApplicationPublications Nos. JP-A 10-270317 and JP-A 1-264220, as shown in FIG. 10Aand FIG. 10B, the autofocus processing is first performed to measure theplanarity of the wafer surface and detect defocused portions, and thenthe exposure scan processing is performed. The scanning is performed ina Y-direction. The exposure position P50 corresponds to the slit. On thesurface 201 of the wafer 200, however, between each of the autofocusbeams 101 disposed in a direction perpendicular to the scan direction,it is not possible to accurately measure the planarity of the surface201 of the wafer 200, so that there is a risk, for example, of thedetection missing a defocused portion.

Even if the movement of the stage is, for example, compensated at thetime of the exposure processing at a part in which there is abnormalplanarity on the wafer surface, it is difficult to compensate other thanfor linear components. For this reason, even if the above-describedautofocus scanning is performed and the stage movement is compensatedbased on information regarding a detected defocused portion, positionsoccur at which it is not possible to perform localized adjustment of thefocus on the wafer surface, the beam becoming defocused at suchpositions, making it impossible to form a normal pattern.

For this reason, with the method of the related art, in the case inwhich there is a partial abnormality in the planarity on the wafersurface, an abnormal pattern remains at this position and is allowed toproceed to the subsequent etching process step. The part of the wafersurface with the pattern abnormality was etched as is, this affectingother normal chips downstream in the manufacturing process.

SUMMARY

In one embodiment, an exposure apparatus may include, but is not limitedto, an autofocus scan processor configured to generate a detectionsignal indicating a defocused portion of a resist film over asemiconductor substrate, an exposure scan processor configured toperform an exposure process for the resist film, and a controllerconfigured to feed back the detection signal from the autofocus scanprocessor to the exposure scan processor.

In another embodiment, an exposure apparatus may include, but is notlimited to, an autofocus scan processor configured to detect a defocusportion of a resist film over a semiconductor substrate by measuringheight-direction positions of the resist film, and to generate adetection signal that indicates the defocus portion, an exposure scanprocessor configured to perform an exposure process for the resist film,the exposure scan processor comprising a selective blinding mechanism;and a controller configured to control the selective blinding mechanismby feeding back the detection signal from the autofocus scan processorto the exposure scan processor.

In yet another embodiment, an exposure apparatus may include, but is notlimited to, an autofocus scan processor configured to perform anautofocus scan processing to measure height-direction positions on asurface of a resist film over a semiconductor wafer, the autofocus scanprocessor being configured to perform a three-dimensional analysis ofinformation of the height-direction positions to generate a detectionsignal indicating a defocused portion of the resist film;

an exposure scan processor including a selective blinding mechanismconfigured to selectively blind the resist film, the exposure scanprocessor configured to perform an exposure process for the resist film;and

a controller configured to receive the detection signal indicating thedefocused portion from the autofocus scan processor, the controllerconfigured to control the selective blinding mechanism to selectivelyblind the resist film with reference to the detection signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will be moreapparent from the following description of certain preferred embodimentstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flow chart illustrating an exposure method for asemiconductor wafer in accordance with an embodiment of the presentinvention;

FIG. 2A is a view illustrating an exposure method for a semiconductorwafer wherein an autofocus scanning process is performed by illuminatinga high density array of beams of light and without blinding when nodefocused portion is present;

FIG. 2B is a graph illustrating a detection signal obtained by theautofocus scanning process shown in FIG. 2A when no defocused portion isdetected;

FIG. 3A is a view illustrating an exposure method for a semiconductorwafer wherein an autofocus scanning process is performed by illuminatinga high density array of beams of light and with blinding when adefocused portion is present;

FIG. 3B is a graph illustrating a detection signal obtained by theautofocus scanning process shown in FIG. 3A when a defocused portion isdetected;

FIG. 4A is a graph illustrating detection signals obtained by theautofocus scanning process when the defocused portion is detected;

FIG. 4B is a plan view illustrating relationships between the detectionsignals of FIG. 4A ad a defocused portion over a semiconductor wafer;

FIG. 5A is a schematic view illustrating blind operations of an exposurescan process, when a defocused portion is detected by an autofocus scanprocess in the semiconductor wafer exposure method using the exposureapparatus in accordance with an embodiment of the present invention;

FIG. 5B is a side view illustrating motion of the blinding plate in theautofocus scan process where the blinding plate does not cover a slit inthe blinding mechanism of FIG. 5A;

FIG. 5C is a side view illustrating motion of the blinding plate in theautofocus scan process where the blinding plate covers the slit in theblinding mechanism of FIG. 5A;

FIG. 5D is a side view illustrating a scanning area of a semiconductorwafer with a defocused portion;

FIG. 6A is a schematic view illustrating a selective blind operations inan exposure scan process, when a defaced portion is detected by anautofocus scan process in the semiconductor wafer exposure method usingthe exposure apparatus in accordance with an embodiment of the presentinvention;

FIG. 6B is a schematic view illustrating non-blind operations of anexposure scan process, when a defaced portion is detected by anautofocus scan process in the semiconductor wafer exposure method usingthe exposure apparatus in accordance with an embodiment of the presentinvention;

FIG. 7A is a view illustrating a selective blind operations in anexposure scan process, when a defaced portion is detected by anautofocus scan process in the semiconductor wafer exposure method usingthe exposure apparatus in accordance with an embodiment of the presentinvention;

FIG. 7B is a view illustrating a selective blind operations in anexposure scan process, when a defaced portion is detected by anautofocus scan process in the semiconductor wafer exposure method usingthe exposure apparatus in accordance with an embodiment of the presentinvention;

FIG. 7C is a view illustrating a selective blind operations in anexposure scan process, when a defaced portion is detected by anautofocus scan process in the semiconductor wafer exposure method usingthe exposure apparatus in accordance with an embodiment of the presentinvention;

FIG. 7D is a cross sectional view of FIGS. 7A, 7B, and 7C;

FIG. 8 is a schematic view illustrating an exposure system including anexposure apparatus including a controller and a storage unit inaccordance with an embodiment of the present invention;

FIG. 9 is a plan view illustrating a reticle used in a case that anegative resist is sued for an exposure method;

FIG. 10A is a view illustrating an exposure method for a semiconductorwafer in related art; and

FIG. 10B is a graph illustrating a detection signal obtained by theautofocus scanning process shown in FIG. 10A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the present invention, the related art will beexplained briefly, in order to facilitate the understanding of thepresent invention.

As described above, in a method of exposing a semiconductor wafer andexposure apparatus according to the related art, it has been difficultto accurately detect a defocused portion using an autofocus scan beforethe exposure scan processing. Also, because either the scanning isstopped or the scanning direction is reversed when a defocused portionis detected, the productivity is reduced. When a defocused portion isdetected, if etching is performed on the abnormal pattern formed at thatposition, because other normal chips are affected in the manufacturingprocess, the yield will decrease.

For this reason, there has been a desire for an exposure method and anexposure apparatus enabling accurate detection of a defocused portionand also enabling manufacture of semiconductor wafers without a drop inproductivity or yield, even if a defocused portion is detected.

Embodiments of the invention will be now described herein with referenceto illustrative embodiments. Those skilled in the art will recognizethat many alternative embodiments can be accomplished using the teachingof the embodiments of the present invention and that the invention isnot limited to the embodiments illustrated for explanatory purpose.

In one embodiment, an exposure method may include, but is not limitedto, the following processes. An autofocus scan process is performed todetect a defocused portion of a first resist film over a semiconductorwafer and to generate a detection signal that indicates the defocusedportion detected. A first exposure scan process is performed whileselectively blinding the first resist film, with reference to adetection signal related to the defocused portion detected.

In some cases, the first resist film may be selectively blinded byselectively blinding the defocused portion.

In some cases, the first resist film may be selectively blinded byselectively blinding other portion of the resist film than the defocusedportion.

In some cases, the autofocus scan process may be performed byilluminating exposure beams of light on the first resist film at ascanning pitch of at most 1 mm.

In some cases, performing the autofocus scan process may include, but isnot limited to, measuring height-direction positions on a surface of thefirst resist film; and performing a three-dimensional analysis ofinformation of the height-direction positions to detect the defocusedportion.

In some cases, performing the first exposure scan process may include,but is not limited to, moving at least a blinding plate to extend acrossan exposure slit and to blind the defocused portion, with reference tothe detection signal.

In some cases, performing the first exposure scan process may furtherinclude, but is not limited to, storing an identification informationidentifying the semiconductor wafer and the information of theheight-direction positions. The at least one of blinding plates is movedwith reference to the identification information and the information ofthe height-direction positions.

In some cases, the method may further include, but is not limited to,removing the first resist film from the semiconductor wafer, forming asecond resist film over the semiconductor wafer, and performing a secondexposure scan process for the second resist film while moving a same atleast one of blinding plates as the at least one of blinding platesmoved in the first exposure scan process, and to blind a same positionof the second resist film as the position blinded in the first exposurescan process, with reference to the identification information and theinformation of the height-direction positions.

In some cases, the method may further include, but is not limited to,removing the first resist film from the semiconductor wafer, forming asecond resist film over the semiconductor wafer, and performing a secondexposure scan process for the second resist film while blinding a sameposition of the second resist film as the position blinded in the firstexposure scan process with reference to the detection signal.

In some cases, performing the autofocus scanning process may furtherinclude, but is not limited to, measuring height-direction positions ona surface of the first resist film, and detecting the defocused portionwith reference to information related to the height-direction positionsmeasured.

In some cases, performing the autofocus scanning process may furtherinclude, but is not limited to, calculating differences between measuredheights and an adjustable height to identify the differences ascalculated defocus values, the measured heights being respectivelydefined by the height-direction positions measured; comparing thecalculated defocus values to a reference defocus value at positions onthe surface of the first resist film; and identifying the defocusedportion at a position where the calculated defocus value exceeds thereference defocus value.

In some cases, performing the autofocus scanning process may furtherinclude, but is not limited to, performing an additional autofocusscanning process which is the same as the autofocus scanning process;determining that the defocused portion is present at the same positionas the position where the defocused portion was identified, if thedefocused portion is identified at the same position when performing theadditional autofocus scanning process; and determining that thedefocused portion is absent at the same position as the position wherethe defocused portion was identified, if the defocused portion is notidentified at the same position when performing the additional autofocusscanning process.

In some cases, performing the autofocus scanning process may furtherinclude, but is not limited to, detecting heights and inclinations ofthe surface of the first resist film from the height-direction positionsmeasured; and detecting the defocused portion with reference to theheights and the inclinations detected.

In some cases, detecting the defocused portion with reference to theheights and the inclinations detected may include, but is not limitedto, calculating high and inclination baselines from the height-directionpositions measured; determining whether a focused plane is offset from abase-plane which is made by the high and inclination baselines; anddetermining whether the focused plane has a three-dimensionally upwardlybulging shape.

In some cases, the first exposure scan process may be performedimmediately after the autofocus scan process is performed.

In another embodiment, an exposure method may include, but is notlimited to, the following processes. Height-direction positions aremeasured on a surface of a first resist film over a semiconductor wafer.Differences are calculated between measured heights and an adjustableheight to identify the differences as calculated defocus values. Themeasured heights are respectively defined by the height-directionpositions measured. The calculated defocus values are compared to areference defocus value at positions on the surface of the first resistfilm. The defocused portion is identified at a position where thecalculated defocus value exceeds the reference defocus value. Adetection signal is generated, which indicates the defocused portiondetected. A first exposure scan process is performed while blinding thedefocused portion, with reference to the detection signal.

In some cases, performing the first exposure scan process may include,but is not limited to, moving at least a blinding plate to extend acrossan exposure slit and to blind the defocused portion, with reference tothe detection signal.

In some cases, performing the first exposure scan process may furtherinclude, but is not limited to, storing an identification informationidentifying the semiconductor wafer and the information of theheight-direction positions. The at least one of blinding plates is movedwith reference to the identification information and the information ofthe height-direction positions.

In still another embodiment, an exposure method may include, but is notlimited to, the following processes. Height-direction positions aremeasured on a surface of a first resist film over a semiconductor wafer.A defocused portion is detected with reference to information related tothe height-direction positions measured. A first exposure scan processis performed while blinding the defocused portion, with reference to thedetection signal.

In some cases, the exposure method may further include, but is notlimited to, detecting heights and inclinations of the surface of thefirst resist film from the height-direction positions measured. Thedetecting the defocused portion may include, but is not limited to,detecting the defocused portion with reference to the heights and theinclinations detected.

In some cases, detecting the defocused portion with reference to theheights and the inclinations detected may include, but is not limitedto, the following processes. High and inclination baselines arecalculated from the height-direction positions measured. A determinationis made on whether a focused plane is offset from a base-plane which ismade by the high and inclination baselines. A determination is made onwhether the focused plane has a three-dimensionally upwardly bulgingshape.

In yet another embodiment, an exposure apparatus may include, but is notlimited to, an autofocus scan processor, an exposure scan processor anda controller. The autofocus scan processor is configured to perform anautofocus scan processing to measure height-direction positions on asurface of a resist film over a semiconductor wafer. The autofocus scanprocessor is configured to perform a three-dimensional analysis ofinformation of the height-direction positions to generate a detectionsignal indicating a defocused portion of the resist film The exposurescan processor includes a selective blinding mechanism that selectivelyblinds the resist film. The exposure scan processor is configured toperform an exposure process for the resist film. The controller isconfigured to receive the detection signal indicating the defocusedportion from the exposure scan processor. The controller is configuredto control the selective blinding mechanism to selectively blind theresist film with reference to the detection signal.

In some cases, the selective blinding mechanism may include, but is notlimited to, an exposure slit and a plurality of blinding plates which ismovable to extend across the exposure slit.

In some cases, the controller is configured to move at least one of theplurality of blinding plates to extend across the exposure slit, withreference to the detection signal, to selectively blind the resist film.

In some cases, the exposure apparatus may further include, but is notlimited to, a defocusing information storage unit configured to store anidentification information identifying the semiconductor wafer andinformation of the height-direction positions.

In some cases, the controller is configured to acquire theidentification information and the information of the height-directionpositions from the defocusing information storage unit. The controlleris configured to move at least one of the plurality of blinding plateswith reference to the identification information and the information ofthe height-direction positions.

First Embodiment

A method of exposing a semiconductor wafer and exposure apparatus thatare embodiments of the present invention are described below, referringto FIG. 1 through FIG. 9. The drawings referenced in the followingdescription are for the purpose of describing embodiments of the methodof exposing a semiconductor wafer and exposure apparatus, and sizes,thicknesses, and other dimensions and the like of various elements shownin the drawings differ from the dimensional relationships in an actualexposure apparatus and the like.

An embodiment of a method of exposing a semiconductor wafer is a method,in manufacturing a semiconductor wafer 1, whereby a photoresist film 2is formed on the semiconductor wafer 1 that has been placed onto anon-illustrated stage, and then exposure scan processing is performedwith respect to the photoresist film 2 using lithography, whereby aresist pattern is formed. Autofocus scan processing that detects adefocused portion 21 on the photoresist film 2 is performed immediatelybefore the exposure scan processing. The exposure scan processing is amethod whereby feedback control that is based on a detection signal forthe defocused portion 21 detected in the autofocus scan processing, theexposure being done while blinding the defocused portion 21 so that theresist pattern is caused to remain at the defocused portion 21 on thesemiconductor wafer 1.

In this embodiment, the case of forming a resist pattern on the surface1 a of the semiconductor wafer 1 by the above-described exposure methodusing an exposure apparatus 10 such as shown in FIGS. 5A, 5B, 5C, and 5Dand FIGS. 6A and 6B, for example, is described herein as an example.

The exposure apparatus 10 for the semiconductor wafer 1 according to thepresent embodiment, after forming a photoresist film 2 onto thesemiconductor wafer 1 placed on a non-illustrated stage, forms a resistpattern by performing lithographic exposure scan processing with respectto the photoresist film 2.

The exposure apparatus 10 is generally configured to include an AF(autofocus) scan processor 30 that recognizes and detects a defocusedportion 21 of the photoresist film 2 on the semiconductor wafer 1, byperforming three-dimensional analysis of the height information obtainedby performing autofocus scan processing to measure the height-directionposition on the surface of the photoresist film 2 immediately before theexposure scan processing; an exposure scan processor 40 that has anexposure slit 41 that passes a beam B of exposure light, and a pluralityof rectangular-shaped blinding plates 42 in a comb-tooth configurationmovably provided in an exposure slit 41 proximal region so that they areperpendicular to the longitudinal direction of the exposure slit 41; anda controller 80 that blinds (blocks the light to) a position along theexposure slit 41 corresponding to a defocused portion 21 by moving atleast one part of the plurality of blinding plates 42 provided on theexposure scan processor 40, based on a detection signal, by feeding backthe detection signal of the defocused portion 21 that has been theoutput from the AF scan processer 30 to the exposure scan processor 40.In the example shown in FIGS. 5A, 5B, 5C, and 5D, the exposure slit 41is provided by the combination of two slitted plates 41A opposing oneanother.

As described above, while there is in recent years an increase in thediameter of semiconductor wafers and an increase in the amount ofsurface area per scan in the lithographic exposure step as acost-reduction consideration, the adoption of micropatterns, the use ofa high numerical aperture, and the use of shorter wavelengths havebrought a narrowing of the DOF margin, thereby increasing the frequencyof occurrence of defocusing. Also, because reduced pattern sizes haveresulted in narrower interconnects, patterns tend to peel away, andthere is risk that the resulting scattering of airborne particles canaffect surrounding normal chips.

With respect to such matters, in the present embodiment the existence orabsence of a defocused portion and the position thereof are detectedfrom information in the autofocus scan processing that is performedimmediately before the lithographic exposure scan processing. Then, whenthe exposure scan processing is performed, blinding is performed in aregion corresponding to a defocused portion within the range of theexposure scan. In this manner, by not exposing a defocused portion onthe semiconductor wafer, it is possible to prevent the occurrence ofpattern peeling and the like, and to avoid affecting surrounding normalchips in subsequent process steps. Additionally, the ID and the positioninformation (region to be blinded) for a semiconductor wafer on which adefocused portion is detected are recorded and managed, to enablelimitation of the exposure light at the defocused portion in subsequentprocessing steps as well, by limiting the exposure light in the sameregion by blinding in all subsequent exposure scan processing steps. Bydoing this, because in subsequent processing, that is, in the formationof the upper layer of the semiconductor wafer, the exposure light islimited in the region that is the same as that of the defocused portionin all exposure steps, the same position of the wafer becomes coveredwith photoresist film, thereby avoiding affecting surrounding normalchips.

The method for exposure of a semiconductor wafer according to thisembodiment is described below in detail.

This embodiment is described by way of a positive-type resist as anexample, in which patterning is performed on the photoresist film 2using lithography, which removes the photoresist film 2 at locationsilluminated by light to form a resist pattern. Such a positive-typeresist pattern (photoresist film) has a very good resolution, enablingthe highly precise formation of micropatterns.

First, in the same manner as in the method of the related art ofexposing a semiconductor wafers, patterning is performed by lithography,and the semiconductor wafer 1, onto the surface of which has been formeda photoresist film 2, is placed onto a non-illustrated stage provided inthe exposure apparatus 10. An alternative procedure is that of placingthe semiconductor wafer 1 onto a stage and then forming the photoresistfilm 2 thereon.

Next, in performing exposure scan processing of the surface 1 a of thesemiconductor wafer 1 in this condition, an autofocus scan is performedimmediately before the exposure scan processing, to detect defocusedportions 21. As the AF scan processor 30 for performing autofocusscanning, it is possible to use a sensor that can optically measure theheight-direction position information on the surface 1 a of thesemiconductor wafer 1 by illuminating it with a scanning bean (beam B).As shown in FIGS. 2A and 2B, the autofocus scan processing is performedsuccessively over the entire surface 1 a of the semiconductor wafer 1.

When doing this, the AF scan processor 30 recognizes and detects adefocused portion 21 of the photoresist film 2 by, for example,performing three-dimensional processing of the height information of thesurface 1 a of the semiconductor wafer 1 by an analysis unit 70, usingthe above-described autofocus scanning. Then, for each measured positionon the surface 1 a of the semiconductor wafer 1, the difference betweenthe results of the height measurement of the surface 1 a and theadjustable height within which compensation is possible by operation ofa stage or the like at the time of exposure is calculated. Thedifference between an actual measured height value and the adjustableheight at the time of exposure is taken as the defocus value at thatposition. At each position on the surface 1 a of the semiconductor wafer1, the defocus value is compared with a precalculated defocus value thatwould result in an improper pattern formation during exposure scanning,and a position having a defocus value that exceeds that value is takento be a defocused portion 21.

FIG. 1 is a flow chart illustrating an exposure method for asemiconductor wafer in accordance with an embodiment of the presentinvention. An autofocus scanning process is performed to detect adefocusing portion of a resist film to generate a detection signal. Thedetection signal is fed back to perform an exposure process withselectively blinding a corresponding portion to a defocusing portion.

As shown in the flowchart of FIG. 1, in step S1, a defocused portion 21is recognized on the surface 1 a of the semiconductor wafer 1 in theautofocus scanning process, the following processing is performed.

First, in step S2, autofocus scanning is performed continuously, and ifa defocused portion is detected at one and the same position in aplurality of scans, in step S3 a judgment is made that it is clear thata defocused portion 21 exists at the detected position. If, in step S5,continuous autofocus scanning is performed, but a subsequent scan doesnot detect the defocused portion 21, in step S6 the judgment is madethat a defocused portion 21 does not exist. In this embodiment, byperforming the processing for recognition and detection of a defocusedportion 21 as shown in FIG. 1, detection accuracy is improved, therebyachieving the effect of improved productivity.

Then, in the case of step S3 in which the judgment has been made that adefocused portion 21 exists at some position on the surface 1 a of thesemiconductor wafer 1, in step S4 the detection signal for detecting thedefocused portion 21 is fed back to the exposure scan processing, andblinding (light blocking) is performed so that exposure scanning is notdone at that part. Specifically, the exposure scan processor 40 of theexposure apparatus 10 is used to performing the following processing,which forms a resist pattern by performing exposure scan processing ofthe photoresist film 2.

First, the detection signal for the defocused portion 21 recognized anddetected using the autofocus scan processing by the AF scan processor 30is fed back, via a controller 80, to the exposure scan processor 40shown in FIG. 5A through FIG. 5D. FIG. 5B shows the normal exposurescanning FIG. 5B shows the blinding exposure scanning As shown in FIG.5A, FIG. 5B, and FIG. 5C, by the controller 80 performing feedbackcontrol, the exposure scan processor 40, based on the detection signalfor the defocused portion 21, causes at least a part corresponding tothe position of the defocused portion 21 among a plurality ofrectangular blinding plates 42 that are disposed in a comb-toothconfiguration in an exposure slit 41 proximal region to moveperpendicularly to the longitudinal direction of the exposure slit 41.By doing this, as shown in FIG. 5D, exposure scanning proceeds as theposition along the exposure slit 41 corresponding to the defocusedportion 21 (refer to FIGS. 3A and 3B and FIGS. 4A and 4B) is blinded bythe blinding plates 42 and the area 1000 of the wafer surface isexposed.

It is preferable in the present embodiment for blinding the exposurescan light is a part of the optical system, that is, a unit that blocksthe exposure slit 41 through which exposure light passes. Also, it ispreferable that the unit to block the exposure slit 41 is such that itblinds at least a part of the exposure slit 41 by moving long, narrowblinding plates 42 arranged in a line at one side of the exposure slit41 in forward and reverse directions using drive mechanism 43, whichuses a piezoelectric effect or the like. If such a method is used, evenif there are defocused portions 21 existing simultaneously in aplurality of areas on the surface 1 a of the semiconductor wafer 1, itis possible to reliably blind all positions that correspond to each ofthe defocused portions 21.

As shown in FIG. 6A and FIG. 6B, a scanning exposure apparatus such asthe exposure apparatus 10 according to the present embodimentilluminates only a part of a reticule by light that passes through theexposure slit 41 and, by controlling the blinding plates 42, blocks apart of the light passing through the exposure slit 41. In FIGS. 6A and6B, P41 represents the exposure position corresponding to the slit 41.When exposing (passing illumination to) a position P41 at which adefocused portion 21 has been detected on the semiconductor wafer 1beforehand by autofocus scanning, a blinding (blocking) operation isperformed at the position corresponding to the defocused portion 21, asshown in FIG. 6A. In contrast, when exposing a position P41 at which thefocus is normal, blocking of the exposure slit 41 is not done, as shownin FIG. 6B.

The unit to block the exposure slit in the present embodiment is notlimited to the above-described blinding plates. For example, as shown inFIG. 7A through FIG. 7D, a half-crescent shaped blinding plate 45 (FIG.7A), a triangular blinding plate 46 (FIG. 7B), or a trapezoidal blindingplate 47 (FIG. 7C) or the like may be used in combination, a methodbeing adopted that moves these blinding plates forward/back andleft/right or rotates them to control the blocking position and size,where FIG. 7D shows the exposure area 1000 of the exposure slit 41.

In the present embodiment, in performing the autofocus scan processingof the surface 1 a of the semiconductor wafer 1 using the AF scanprocessor 30, from the standpoint of enabling accurate and thoroughdetection of defocused portions, it is preferable, as shown in FIGS. 3Aand 3B and FIGS. 4A and 4B, that the beam B that is caused to strike thephotoresist film 2 on the semiconductor wafer 1 strikes with beamsarranged to have a density with a scan pitch of 1 mm or smaller. Thedefocused portion 21 is illustrated in FIGS. 3A, 3B, 4A and 4B.

In this case, as shown in FIG. 3A and FIG. 3B, a plurality of beams Bare arranged in the width direction with respect to the scan direction.The surface 1 a is subjected to autofocus scanning by the beam Bimmediately before exposure scanning, where a plurality of beam Bstriking points are disposed on the surface 1 a. Then, as shown in FIG.4A and FIG. 4B, by performing the autofocus scan with the plurality ofbeams B arranged with high density, the height D1 and inclination θ onthe surface 1 a are detected from the surface positions detected at eachstriking point, by detection of the presence or absence of defocusingwith high precision, enabling feedback control.

In the present embodiment, by concentrating the arrangement density ofthe beam B, which performs an autofocus scan immediately before theexposure scan, on many points with a scanning pitch of 1 mm or smaller,it is possible to perform reliable detection of even smaller defocusing.In the present embodiment, with regard to the judgment criterion forexistence or absence of defocusing when performing the autofocusscanning with the beam B striking points arranged with a density asmentioned above, the following setting can be made.

(a) the case in which, upon performing a least-squares calculation ofthe height and inclination baseline from surface positions detected by alarge number of beam striking points and performing a comparison withthis baseline, there are continuous detections of a point at which thefocus is upwardly convex and also exceeds the allowable DOF for thisprocess step (reticule).

(b) the case in which continuous points at which defocusing occurs aredetected continuously in the autofocus scanning direction as well.

In the case in which the above-described cases (a) and (b) occursimultaneously, that is, the case in which the focus plane is offsetfrom the base plane in only a certain area within the autofocus scanrange, if there is a three-dimensionally upwardly bulging shape, it ispossible to judge that defocusing exists within that shot.

In the present embodiment, in performing the autofocus scan and theexposure scan using an exposure apparatus 10 configured as mentionedabove, the constitutions of the focus mechanism and the blinding platedriver used in the exposure apparatus 10 are not particularlyrestricted. With regard to the focus mechanism, the blinding plate drivemechanism and the like in the present embodiment, it is possible to usethe related art, for example as recited in Japanese Patent ApplicationPublication No. JP-A 10-270317.

Also, in the present embodiment as shown in FIG. 8, the above-describedexposure scan processing may further adapt a configuration in which theID and the position information for a semiconductor wafer 1 on which adefocused portion 21 has occurred is acquired by a controller 80provided in the exposure apparatus 10 by using an analysis unit 70 andthe controller 80 then stores the data in a defocusing informationstorage unit 50 such as a server or the like. In this case, thecontroller 80 provided in the exposure apparatus 10 acquires the ID andposition information for a semiconductor wafer 1 on a defocused portion21 has occurred, which the defocusing information storage unit 50 hadstored. The controller 80 sends the ID and position information to theexposure scan processor 40. Then, based on the semiconductor wafer 1 IDand position information, as shown in FIG. 5A through FIG. 5D, at leasta part of the plurality of blinding plates 42 provided in the exposurescan processor 40 are caused to move so as to perform exposure scanningwhile blinding a position along the exposure slit 41 corresponding to adefocused portion 21.

By adopting the above-described constitution, when the occurrence ofdefocusing is detected midway in the manufacturing process of asemiconductor wafer, it is possible in subsequent process steps to limitthe exposure in the same region by automatic blinding operations,regardless of whether there is defocusing or not in subsequent exposurescan processing steps. In the example shown in FIG. 8, after detectionof a defocused portion 21 on the semiconductor wafer 1 in thelithography step 1 (S11), in all of the subsequent lithography steps 2through 4 (S12, S13 and S14), exposure scanning is performed whileblinding the position corresponding to the defocused portion 21. In thismanner, when a defocused portion is detected, by limiting exposure inall subsequent steps in which exposure scanning is performed, the waferbecomes covered with photoresist film in the same position in the planardirection, so that it is possible to avoid affecting surrounding normalchips.

If the present embodiment is applied not to the patterning of aphotoresist film as used to describe this embodiment, but rather to thesemiconductor wafer base process steps, because chips in that part donot perform prescribed circuit operations, it is preferable that thatpart be covered with a photoresist film in subsequent process steps.

When performing lithographic exposure scan processing in thisembodiment, scanning information regarding the occurrence of a defocusedportion is instantaneously detected from the immediately prior autofocusscan processing information, and blinding is performed that limits theexposure over a range corresponding to the defocused portion. By notexposing a defocused portion on a semiconductor wafer in this manner,peeling of interconnect patterns is prevented, and affecting surroundingnormal chips in subsequent process steps is avoided. Additionally, byrecording and managing the ID and position information for asemiconductor wafer on which a defocused portion has occurred at thestart of manufacturing and limiting exposure of the same regions byblinding, it is possible by limiting the exposure in the defocusedportion in subsequent process steps to avoid having this matter extendeven to surrounding normal chips.

In the related art, when skipping exposure scanning in units ofsemiconductor chips is performed, a photoresist film (with nopatterning) remains so as to cover the semiconductor chips for one shotof exposure (all the semiconductor chips existing on the photomask andfound simultaneously), and in exposure developing and dry etching, thepattern precision of neighboring chips was affected. For this reason,with the adoption of micropatterns in semiconductors as seen in recentyears, there has been a desire that there be no locations on asemiconductor wafer having non-uniform patterning.

In the present embodiment, by blinding (blocking light) as describedabove, a position at which defocusing occurs is covered with aphotoresist film with pinpoint precision. By intentionally not formingpatterns on a defocused portion on a semiconductor wafer in this manner,because the defocused portion is not etched, it is possible to reducethe effect to surrounding normal chips by element pattern peeling andthe effect on subsequent process steps.

In the present embodiment, by detecting a defocused portion by autofocusscanning and blinding the part simultaneously with the exposure scan, itis possible to prevent a reduction of throughput and to improveproductivity.

Additionally, in the present embodiment, by adopting a constitution inwhich the defocused portion detection signal Sd21 is stored as thesemiconductor wafer ID and position information in a defocusinginformation storage unit that is a server or the like, it is possible toavoid adversely affecting all subsequent process steps.

Although this embodiment is mainly described using the example offorming positive-type resist, the method of exposing a semiconductorwafer and exposure apparatus of the present embodiment are not limitedin that manner, and can be applied also a negative-type resist.

In such cases, a transparent region 62 (region in which there is nopattern) having a width that is the same as that of the usual exposureregion 61 (region of the chip having a pattern) is provided at the endpart of the reticule 60, as shown in FIG. 9. In the case of forming anegative-type resist on a semiconductor wafer, rather than performingthe above-described blinding operation, exposure is first done over theentire region of the semiconductor wafer, and the chip is patterned,after which movement is performed to a chip at a defocused portion onthe wafer that had previously been detected, and the defocused portiononly is illuminated with light, with an aperture opened at only a partof the light-passing region 62 of the reticule. When this is done, anexposure region 61 on the reticule having a pattern of a chip iscompletely blocked from light by a blinding mechanism having aconstitution differing from that in the above-described embodiment.

A blinding mechanism similar to the one described in the above-describedembodiment may be used for opening only a part of the light-passingregion 62. If this method is used, by striking the defocused portionwith light, the negative-type resist can be caused to remain so as tocover that location.

As described above, according to the exposure method for thesemiconductor wafer 1 of the present embodiment, in addition to theabove-described constitution enabling accurate detection of a defocusedportion 21, when performing exposure during the exposure scan processingto expose regions that include a region in which defocusing occurs,because exposure illumination is not done on the defocused portion 21,it is possible to leave a resist pattern so as to cover only thedefocused portion 21. By doing this, in subsequent process steps thedefocused portion 21 is not subjected to etching, while it is possibleto perform precise etching of the parts other than the defocused portion21. Therefore, even in the case of exposure scanning of a semiconductorwafer 1 that includes a defocused portion 21, abnormalities of theinterconnect pattern or holes, which are caused by abnormalities in theresist pattern in the defocused portion 21, do not occur, andsurrounding normal chips are not affected, making it possible tomanufacture the semiconductor wafer 1 without a decrease in productivityand yield.

According to the exposure apparatus 10 for the semiconductor wafer 1 ofthe present embodiment, by the above-described constitution, becauseexposure illumination is not done at the defocused portion 21 during theexposure scan processing, it is possible to leave a resist pattern thatcovers only the defocused portion 21, so that the defocused portion 21is not etched in subsequent process steps, and so that the regions otherthan the defocused portion 21 are properly etched. Therefore, similar towhat is described above, abnormalities of the interconnect pattern orholes, which are caused by abnormalities in the resist pattern in thedefocused portion 21, do not occur, and surrounding normal chips are notaffected, making it possible to manufacture the semiconductor wafer 1without a decrease in productivity and yield.

As used herein, the following directional tennis “forward, rearward,above, downward, vertical, horizontal, below, and transverse” as well asany other similar directional terms refer to those directions of anapparatus equipped with the present invention. Accordingly, these terms,as utilized to describe the present invention should be interpretedrelative to an apparatus equipped with the present invention.

The term “configured” is used to describe a component, section or partof a device includes hardware and/or software that is constructed and/orprogrammed to carry out the desired function.

Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments.

The terms of degree such as “substantially,” “about,” and“approximately” as used herein mean a reasonable amount of deviation ofthe modified term such that the end result is not significantly changed.For example, these terms can be construed as including a deviation of atleast ±5 percents of the modified term if this deviation would notnegate the meaning of the word it modifies.

It is apparent that the present invention is not limited to the aboveembodiments, but may be modified and changed without departing from thescope and spirit of the invention.

What is claimed is:
 1. An exposure apparatus comprising: an autofocusscan processor configured to generate a detection signal indicating adefocused portion of a resist film over a semiconductor substrate; anexposure scan processor configured to perform an exposure process forthe resist film; and a controller configured to feed back the detectionsignal from the autofocus scan processor to the exposure scan processor.2. The exposure apparatus according to claim 1, wherein the controlleris configured to feed back the detection signal so that the defocusedportion of the resist film is selectively blinded.
 3. The exposureapparatus according to claim 1, wherein the controller is configured tofeed back the detection signal so that a portion of the resist filmother than the defocused portion is selectively blinded.
 4. The exposureapparatus according to claim 1, wherein the autofocus scan processor isfurther configured to illuminate exposure beams of light on the resistfilm at a scanning pitch of at most 1 mm.
 5. The exposure apparatusaccording to claim 1, wherein the autofocus scan processor is furtherconfigured to measure height-direction positions on a surface of theresist film, and wherein the autofocus scan processor is furtherconfigured to perform a three-dimensional analysis of information of theheight-direction positions to detect the defocused portion.
 6. Theexposure apparatus according to claim 5, wherein the exposure scanprocessor is further configured to move at least one of blinding platesto extend across an exposure slit, and wherein the exposure scanprocessor is further configured to blind the defocused portion withreference to the detection signal.
 7. The exposure apparatus accordingto claim 6, wherein the exposure scan processor is further configured tostore an identification information identifying the semiconductor waferand the information of the height-direction positions, and wherein atleast one of the blinding plates is configured to move with reference tothe identification information and the information of theheight-direction positions.
 8. The exposure apparatus according to claim1, wherein the autofocus scan processor is further configured to measureheight-direction positions on a surface of the resist film, and whereinthe autofocus scan processor is further configured to detect thedefocused portion with reference to information related to theheight-direction positions measured.
 9. The exposure apparatus accordingto claim 8, wherein the autofocus scan processor is further configuredto calculate differences between measured heights and an adjustableheight to identify the differences as calculated defocus values, themeasured heights being respectively defined by the height-directionpositions measured, wherein the autofocus scan processor is furtherconfigured to compare the calculated defocus values to a referencedefocus value at positions on the surface of the resist film, andwherein the autofocus scan processor is further configured to identifythe defocused portion at a position where the calculated defocus valueexceeds the reference defocus value.
 10. The exposure apparatusaccording to claim 9, wherein the autofocus scan processor is furtherconfigured to detect heights and inclinations of the surface of theresist film from the height-direction positions measured, and whereinthe autofocus scan processor is further configured to detect thedefocused portion with reference to the heights and the inclinationsdetected.
 11. The exposure apparatus according to claim 10, wherein theautofocus scan processor is further configured to calculate high andinclination baselines from the height-direction positions measured,wherein the autofocus scan processor is further configured to determinewhether a focused plane is offset from a base-plane which is made by thehigh and inclination baselines, and wherein the autofocus scan processoris further configured to determine whether the focused plane has athree-dimensionally upwardly bulging shape.
 12. An exposure apparatuscomprising: an autofocus scan processor configured to detect a defocusportion of a resist film over a semiconductor substrate by measuringheight-direction positions of the resist film, and to generate adetection signal that indicates the defocus portion; an exposure scanprocessor configured to perform an exposure process for the resist film,the exposure scan processor comprising a selective blinding mechanism;and a controller configured to control the selective blinding mechanismby feeding back the detection signal from the autofocus scan processorto the exposure scan processor.
 13. The exposure apparatus according toclaim 12, wherein the controller is configured to selectively blind thedefocused portion of the resist film with reference to the detectionsignal.
 14. The exposure apparatus according to claim 12, wherein theselective blinding mechanism comprises a blinding plate to extend acrossan exposure slit and to blind the defocused portion.
 15. The exposureapparatus according to claim 14, wherein the blinding plate comprises atleast one of narrow blinding plates arranged in a line at one side ofthe exposure slit, a half-crescent shaped blinding plate, a triangularblinding plate, and a trapezoidal blinding plate.
 16. An exposureapparatus comprising: an autofocus scan processor configured to performan autofocus scan processing to measure height-direction positions on asurface of a resist film over a semiconductor wafer, the autofocus scanprocessor being configured to perform a three-dimensional analysis ofinformation of the height-direction positions to generate a detectionsignal indicating a defocused portion of the resist film; an exposurescan processor including a selective blinding mechanism configured toselectively blind the resist film, the exposure scan processorconfigured to perform an exposure process for the resist film; and acontroller configured to receive the detection signal indicating thedefocused portion from the autofocus scan processor, the controllerconfigured to control the selective blinding mechanism to selectivelyblind the resist film with reference to the detection signal.
 17. Theexposure apparatus according to claim 16, wherein the selective blindingmechanism comprises an exposure slit and a plurality of blinding plateswhich is movable to extend across the exposure slit.
 18. The exposureapparatus according to claim 17, wherein the controller controls to moveat least one of the plurality of blinding plates to extend across theexposure slit to selectively blind the resist film with reference to thedetection signal.
 19. The exposure apparatus according to claim 17,further comprising a defocusing information storage unit storing anidentification information identifying the semiconductor wafer.
 20. Theexposure apparatus according to claim 19, wherein the controlleracquires the identification information from the defocusing informationstorage unit, and wherein the controller controls to move at least oneof the plurality of blinding plates with reference to the identificationinformation.